A shaft train in fluid-flow machines, such as in a power plant, can be excited to vibrate as the shaft train rotates. The vibrations of the shaft train are disadvantageous, however, since they shorten the service life of the shaft train.
With the aid of a clutch, the shaft train can be subdivided into sub-shafts, wherein the sub-shafts can rotate independently of one another when decoupled and rotate together when coupled. For example, a sub-shaft can have a gas turbine, with the waste heat from which a steam turbine of the other sub-shaft is driven. When the gas turbine is started up, there is not yet sufficient waste heat available to drive the steam turbine. In order to suppress ventilation within the steam turbine, the two sub-shafts are conventionally coupled to each other only when the sub-shaft having the steam turbine has been accelerated to the rotational speed of the sub-shaft having the gas turbine. Likewise, for example, in a combined heat and steam power plant, two sub-shafts each having a steam turbine can be coupled and uncoupled by means of a clutch. When a large quantity of steam is removed for a discharge of heat from the combined heat and steam power plant, the sub-shafts can be uncoupled, so that steam does not have to flow through one of the two steam turbines.
It has transpired that the vibratory behavior of the shaft train depends on the coupling angle of the two sub-shafts. Conventionally, the two sub-shafts are repeatedly uncoupled and coupled until a desired target coupling angle with a low vibratory loading is established. Here, however, the desired target coupling angle is only achieved by accident and, at the same time, also only with a low degree of accuracy.